1. Field of the Invention
The energy of ocean waves is immense and one of the largest renewable resources of energy that can be harvested by mankind. The US DOE estimate that the total power of waves breaking on the world's coastlines is 2 to 3 billion kW. Ocean wave energy is useful to mankind not only due to its energetic potential but also, unlike wind, is less intermittent as it is not reliant on local weather conditions and may travel thousands of miles with little energy dissipation.
2. Description of the Prior Art
There have been many attempts to harvest wave energy. The main problems being:
1) The energy of the waves is greatest in open sea far from shore, for example in some areas off the North Atlantic ridge swell heights can average about 8 meters. Closer to shore, wave energy is dissipated due to bottom friction and diffraction effects. Under deep-water conditions installation of wave energy converters can be difficult and expensive. Shore based wave energy converters are easier to install but have lower theoretical capacity and a greater environmental impact.
2) Many wave energy converters use floats that bob up and down on the wave with relation to the seabed, this movement may be used to generate electricity. However these type of energy converters intrinsically only harvest a small proportion of the wave's energy even if erected in open sea.
3) A wave's energy could be regarded as linear, perpendicular and/or parallel to the gravity of the earth. The energy that is parallel to the earth's gravity can be looked at as alternating in direction. Some of the most common electricity generating methods are based on force moving in one direction that creates a rotation of magnets or coils of wire about a central axis (a generator or turbine). Many methods for converting wave energy to electrical energy, particularly float based systems, have low efficiencies when attempting to convert alternating linear energy to the unidirectional rotation of a generator shaft.
A successful ocean wave energy converter could therefore comprise some or all of the following. It should function whatever the direction of the waves, it should harvest a large amount of the total energy of the wave, it should convert the force of the wave of alternating direction to unidirectional rotation of a generator shaft and it should be relatively simple to construct in open sea and deep water.